What is Multiarch?

In order to ease cross-compiling and distribution, the Debian-based distros have undertaken a project known as "multi-arch." The idea is to update the packaged software itself, and occasionally change how it's built, so that every package can satisfy multiple architectures. Either one version of the package will work for all architectures, or the different architectures' versions can be installed alongside each other.

To be fully compliant, a package not only needs to play well with different architectures, but explicitly state how it operates in a multi-arch environment. This is implemented through values in the control file of each source package, which are then enforced by the distro's package management.

While there are general guidelines, each package has its own dynamic so making it multi-arch compatible is largely up to that package's maintainer. As a result, multi-arch is still a work in progress, and the distros prioritize which packages they focus on.

According to documents from ca. 2013, multi-arch behavior for header-files (common in -dev packages) was undefined. Since then, the Debian-family distros have settled on using subdirectories for multi-arch triplets within /usr/include/. Note that this extension is not yet part of the Filesystem Hierarchy Standard.

Status of Wine Build Dependencies

Perhaps the main (but not only) way this matters to Wine is in regards to building and porting. Once all of Wine's build dependencies are multi-arch compatible, cross-compiling and packaging Wine for different architectures becomes much simpler.

As of September 2017, building Wine 2.17 on Debian Stretch shows the following build dependencies still conflicting across architectures (version info may be different for Ubuntu, Mint, etc.)

Several of these packages will be fixed in Debian Buster, or only conflict because of dependencies that will be. When Debian Buster is released, we can remove them from the table.

I determined these packages by simulating apt-get build-dep with i386 build-dependencies for the (Debian unstable) version of wine-development:

apt-get -s build-dep wine-development/unstable -a i386

At first, this would return an error for some package; to bypass the error, I used apt-get source to grab the package source, quickly entered a "Multi-Arch: foreign" key into the control file, then rebuilt and installed it. After repeating this for a few packages, the simulated apt-get completed. I didn't need these packages to actually work, only to install and allow apt-get to give a full build-dep list.

See Also

Some of these pages might be out of date, but they're still good places to start: